The invention relates to trolley wheels, and more particularly to trolley wheels for an overhead load lifting apparatus such as a monorail hoist. Conventional overhead lifting apparatus such as monorail hoists include trolleys supported by trolley wheels that ride on a rail. Typically, the rail is some variation of an I-beam that includes a substantially horizontal supporting surface with a flat tread supporting surface on which a trolley wheel rolls. To keep the wheel in the proper position on the tread supporting surface, the wheel includes a flange. If the wheel deviates too far from the proper rolling position on the rail, the flange contacts the sidewall of the rail and forces the wheel to move back into the proper rolling position.
While the tread surface of a trolley wheel is often flat, it has been known to crown the tread surface to produce better rolling contact with the supporting surface of the rail. It is also common to linearly taper the flange of the trolley wheel such that only the flange portion nearest the tread surface would ever contact the sidewall of the rail. Examples of these types of trolley wheels are disclosed in U.S. Pat. Nos. 4,236,456 issued to Schreyer et al., 2,997,996 issued to Chapin et al., 2,584,610 issued to Pearson, and 1,367,706 issued to Loudenslager.
It has also been known to use a gradual non-linear tapering on the flange of the trolley wheel. An example of this type of trolley wheel is disclosed in U.S. Pat. No. 1,869,422 issued to Harris.